High Alloy Steel Pipe Cold Rolling Yield Strength Control
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Solution Overview
Problem
Existing methods for producing high alloy pipes for deep oil wells in severe corrosive environments do not adequately address the need for both high strength and corrosion resistance, particularly in terms of yield strength, and lack specific composition design and cold working conditions to achieve targeted strength.
Innovation Solution
A method involving high alloy pipes with a chemical composition of 20-30% Cr and 25-40% Ni, with reduced C content, subjected to hot working and optional solid-solution heat treatment, followed by cold rolling with a working ratio of 30-80% reduction in area, where the yield strength is calculated using specific formulas to achieve targeted yield strength of 758.3 to 965.2 MPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cold working is performed to increase strength, then yield strength is improved, but ductility and toughness are deteriorated when working ratio exceeds 80%
Solution Approach 1:
The patent optimizes the working ratio parameter to a specific range (30-80% reduction of area) to achieve the desired yield strength while preventing excessive work hardening that would deteriorate ductility and toughness. This parameter optimization resolves the contradiction by identifying the optimal working ratio range.
Solution Approach 2:
The patent introduces dynamic control of the cold working process by specifying precise working ratio ranges and allowing adjustment based on composition variations. The working ratio is dynamically optimized based on the interrelation between composition elements and mechanical properties.
2Reliability
If alloy composition is adjusted to improve corrosion resistance, then corrosion resistance is improved, but strength may be insufficient without additional processing
Solution Approach 1:
The patent combines composition optimization with cold working processing to achieve both corrosion resistance and high strength. The synergistic effect of controlled alloy composition and optimized cold working (30-80% reduction of area) produces pipes that satisfy both requirements simultaneously.
Solution Approach 2:
The patent creates a composite microstructure through controlled composition and cold working, resulting in a material that exhibits both corrosion resistance from the alloy composition and high strength from the work-hardened microstructure.
3Strength
If cold working is performed with high working ratio to achieve high strength, then yield strength increases, but work hardening occurs and ductility deteriorates
Solution Approach 1:
The patent changes the working ratio parameter from unlimited high values to a controlled range (30-80% reduction of area) to prevent excessive work hardening while maintaining high strength. This parameter control makes the manufacturing process more manageable and predictable.
4Strength
If alloy composition is optimized for strength, then strength is improved, but corrosion resistance may be compromised
Solution Approach 1:
The patent merges composition optimization with cold working processing to achieve both strength and corrosion resistance. The controlled cold working (30-80% reduction of area) enhances strength through work hardening while the base composition maintains corrosion resistance, avoiding the need to compromise either property.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of high alloy pipes with the required corrosion resistance and targeted strength without excessive alloying components, allowing for the regulation of yield strength through working ratio and composition, reducing material costs and overstock.
Implementation Method 1
by a hot working and optionally by a solid-solution heat treatment
Implementation Method 2
by a hot working and optionally by a solid-solution heat treatment
Implementation Method 3
by subsequently subjecting the high alloy material pipe to a cold rolling
Implementation Method 4
the working ratio Rd, in terms of the reduction of area, in the final cold rolling step falls within a range of larger than 30% and equal to or less than 80%
Data Source
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AI summary
Problem to be Solved: A high alloy pipe can be produced that has not only a corrosion resistance required for oil well pipes but also has a targeted strength, without excessively adding alloying components, by selecting the working conditions at the time of the cold rolling. Solution: A method for producing a high alloy pipe having a minimum yield strength of 758.3 to 965.2 MPa, comprising: preparing a high alloy material pipe having a chemical composition consisting, by mass%, of C: 0.03% or less, Si: 1.0% or less, Mn: 0.3 to 5.0%, Ni: 25 to 40%, Cr: 20 to 30%, Mo: 0 to 4%, Cu: 0 to 3% and N: 0.05 to 0.50%, and the balance being Fe and impurities, by a hot working and optionally by a solid-solution heat treatment; and producing the high alloy pipe by subsequently subjecting the high alloy material pipe to a cold rolling, wherein the cold rolling is performed under the conditions that the working ratio Rd, in terms of the reduction of area, in the final cold rolling step falls within a range of larger than 30% and equal to or less than 80%, and the following formula (1) is satisfied: Rd%≥MYS-520/3.1-Cr+6×Mo+300×N wherein Rd and MYS signify the working ratio (%) in terms of the reduction of area and the targeted yield strength (MPa), respectively, and Cr, Mo and N signify the contents (mass%) of the individual elements, respectively.